Havn't seen it yet so can't really judge, but wasn't it said they were scared to even use the character for racist reasons? The IM3 take is still getting criticized by fans on just about every forum but the film seems to be liked for being well made regardless. I think the quality of the film is what matters the most for any studio.

Doom, Galactus, Cyclops, Rogue, Deadpool etc are all more well known then The Mandarin and appeared in ****** movies. So it's not really a surprise that Fox gets the heat more for their films then one character in Iron Man 3 does. Fox have made just plain bad decisions on 4 of their Marvel flicks that generally weren't very good or just sucked. Their percentage is not good. If the MCU was putting out bad films instead of crowd pleasing well reviewed ones, then the hate would be huge.